Buggy code:
private SEMICOLON = new char [ ] { ';' } ; private static final char [ ] CLASS = "Class" . toCharArray ( ) ; private static final char [ ] VOID = "void" . toCharArray ( ) ; private static final char [ ] INT = "int" . toCharArray ( ) ; private static final char [ ] INT_SIGNATURE = new char [ ] { Signature . C_INT } ; private static final char [ ] VALUE = "value" . toCharArray ( ) ; private static final char [ ] EXTENDS = "extends" . toCharArray ( ) ; private static final char [ ] SUPER = "super" . toCharArray ( ) ; private static final char [ ] VARARGS = "..." . toCharArray ( ) ; private static final char [ ] IMPORT = "import" . toCharArray ( ) ; private static final char [ ] STATIC = "static" . toCharArray ( ) ; private static final char [ ] ON_DEMAND = ".*" . toCharArray ( ) ; private static final char [ ] IMPORT_END = ";\n" . toCharArray ( ) ; private static final char [ ] JAVA_LANG_OBJECT_SIGNATURE = CompletionEngine . createTypeSignature ( CharOperation . concatWith ( TypeConstants . JAVA_LANG , '.' ) , TypeConstants . OBJECT ) ; private static final char [ ] JAVA_LANG_NAME = CharOperation . concatWith ( TypeConstants . JAVA_LANG , '.' ) ; private static final int NONE = 0 ; private static final int SUPERTYPE = 1 ; private static final int SUBTYPE = 2 ; private static final int FIELD = 0 ; private static final int LOCAL = 1 ; private static final int ARGUMENT = 2 ; int expectedTypesPtr = - 1 ; TypeBinding [ ] expectedTypes = new TypeBinding [ 1 ] ; int expectedTypesFilter ; boolean hasJavaLangObjectAsExpectedType = false ; int uninterestingBindingsPtr = - 1 ; Binding [ ] uninterestingBindings = new Binding [ 1 ] ; int forbbidenBindingsPtr = - 1 ; Binding [ ] forbbidenBindings = new Binding [ 1 ] ; int forbbidenBindingsFilter ; ImportBinding [ ] favoriteReferenceBindings ; boolean assistNodeIsClass ; boolean assistNodeIsEnum ; boolean assistNodeIsException ; boolean assistNodeIsInterface ; boolean assistNodeIsAnnotation ; boolean assistNodeIsConstructor ; boolean assistNodeIsSuperType ; int assistNodeInJavadoc = 0 ; boolean assistNodeCanBeSingleMemberAnnotation = false ; long targetedElement ; IJavaProject javaProject ; CompletionParser parser ; CompletionRequestor requestor ; CompletionEngine . CompletionProblemFactory problemFactory ; ProblemReporter problemReporter ; char [ ] source ; char [ ] completionToken ; char [ ] qualifiedCompletionToken ; boolean resolvingImports = false ; boolean resolvingStaticImports = false ; boolean insideQualifiedReference = false ; boolean noProposal = true ; CategorizedProblem problem = null ; char [ ] fileName = null ; int startPosition ; int actualCompletionPosition ; int endPosition ; int offset ; int javadocTagPosition ; HashtableOfObject knownPkgs = new HashtableOfObject ( 10 ) ; HashtableOfObject knownTypes = new HashtableOfObject ( 10 ) ; Scanner nameScanner ; static final BaseTypeBinding [ ] BASE_TYPES = new BaseTypeBinding [ ] { TypeBinding . BOOLEAN , TypeBinding . BYTE , TypeBinding . CHAR , TypeBinding . DOUBLE , TypeBinding . FLOAT , TypeBinding . INT , TypeBinding . LONG , TypeBinding . SHORT , TypeBinding . VOID } ; static final int BASE_TYPES_LENGTH = CompletionEngine . BASE_TYPES . length ; static final char [ ] [ ] BASE_TYPE_NAMES = new char [ CompletionEngine . BASE_TYPES_LENGTH ] [ ] ; static final int BASE_TYPES_WITHOUT_VOID_LENGTH = ( CompletionEngine . BASE_TYPES . length ) - 1 ; static final char [ ] [ ] BASE_TYPE_NAMES_WITHOUT_VOID = new char [ CompletionEngine . BASE_TYPES_WITHOUT_VOID_LENGTH ] [ ] ; static final char [ ] classField = "class" . toCharArray ( ) ; static final char [ ] lengthField = "length" . toCharArray ( ) ; static final char [ ] cloneMethod = "clone" . toCharArray ( ) ; static final char [ ] THIS = "this" . toCharArray ( ) ; static final char [ ] THROWS = "throws" . toCharArray ( ) ; static InvocationSite FakeInvocationSite = new InvocationSite ( ) { public TypeBinding [ ] genericTypeArguments ( ) { } public boolean isSuperAccess ( ) { } public boolean isTypeAccess ( ) { } public void setActualReceiverType ( ReferenceBinding receiverType ) { } public void setDepth ( int depth ) { } public void setFieldIndex ( int depth ) { } public int sourceStart ( ) { } public int sourceEnd ( ) { } } ; private ObjectVector acceptedTypes ; public CompletionEngine ( SearchableEnvironment nameEnvironment , CompletionRequestor requestor , Map settings , IJavaProject javaProject ) { } public void acceptType ( char [ ] packageName , char [ ] simpleTypeName , char [ ] [ ] enclosingTypeNames , int modifiers , AccessRestriction accessRestriction ) { } private void acceptTypes ( Scope scope ) { } public void acceptUnresolvedName ( char [ ] name ) { } private final boolean areParametersCompatibleWith ( TypeBinding [ ] parameters , TypeBinding [ ] arguments , boolean isVarargs ) { } private void proposeType ( char [ ] packageName , char [ ] simpleTypeName , int modifiers , int accessibility , char [ ] typeName , char [ ] fullyQualifiedName , boolean isQualified , Scope scope ) { char [ ] completionName = fullyQualifiedName ; if ( isQualified ) { if ( ( packageName == null ) || ( ( packageName . length ) == 0 ) ) if ( ( ( this . unitScope ) != null ) && ( ( this . unitScope . fPackage . compoundName ) != ( CharOperation . NO_CHAR_CHAR ) ) ) return ; } else { completionName = simpleTypeName ; } TypeBinding guessedType = null ; if ( ( ( ( modifiers & ( ClassFileConstants . AccAnnotation ) ) != 0 ) && ( this . assistNodeIsAnnotation ) ) && ( ( ( this . targetedElement ) & ( TagBits . AnnotationTargetMASK ) ) != 0 ) ) { char [ ] [ ] cn = CharOperation . splitOn ( '.' , fullyQualifiedName ) ; TypeReference ref ; if ( ( cn . length ) == 1 ) { ref = new SingleTypeReference ( simpleTypeName , 0 ) ; } else { ref = new QualifiedTypeReference ( cn , new long [ cn . length ] ) ; } switch ( scope . kind ) { case Scope . METHOD_SCOPE : case Scope . BLOCK_SCOPE : guessedType = ref . resolveType ( ( ( BlockScope ) ( scope ) ) ) ; break ; case Scope . CLASS_SCOPE : guessedType = ref . resolveType ( ( ( ClassScope ) ( scope ) ) ) ; break ; } <START_BUG> if ( ! ( guessedType . isValidBinding ( ) ) ) <END_BUG>

Fix:
if ( ( guessedType == null ) || ( ! ( guessedType . isValidBinding ( ) ) ) )